niewod@madryt:~/System$rox -v
ROX-Filer 2.5
Copyright (C) 2005 Thomas Leonard.
ROX-Filer comes with ABSOLUTELY NO WARRANTY,
to the extent permitted by law.
You may redistribute copies of ROX-Filer
under the terms of the GNU General Public License.
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This tip dates from the Good Old Days of using AVFS and its "rewrite" module to access archive contents. back then a kernel module translated pathnames with a # in them into ones within the AVFS filesystem. Nowadays this module is unavailable, so we need to do things a little differently.

The modern equivalent (using AVFS+FUSE, assuming that you have a ~/.avfs directory and have already executed mountavfs) would be to set the run action to rox "$HOME/.avfs$@#/"

For what it's worth, I actually set the run action to a script that reads like this: